in principle
原则上; 基本上as far as basic principles are concerned; in general but not in detail
Her idea is sound in principle.从原则上来说,她的观点是正确的。
They are agreed in principle but not in detail.他们的看法在大体上是一致的,但是在细节上有所不同。
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on principle
依据自己的原则〔所确定的信念〕according to one's principles or a fixed belief
He refused on principle to agree to the terms of the treaty.根据自己的道德观念,他拒绝同意条约上的条款。
He drank hot milk every night on principle.他照例每晚必饮热牛奶。

Each side declared that it would never abandon its principle.各方都说绝不放弃自己的原则。
He has no principles at all.他毫无信念可言。
He is quite without principle.他完全没有道德观念。

principle, doctrine
这两个名词的共同意思是“信条”“准则”。principle指一切党派、学科的基本原则和原理; doctrine则指宗教的教义、宗旨等,由信仰所决定,不能更改。

［同义词］   belief, honor, rule, standards
［反义词］   dishonesty, dishonor, immorality